Many assembly operations require the loading of one or more parts into an assembly fixture, or jig, prior to a subsequent manufacturing step, such as welding. To reduce manufacturing costs, typically the loading of the parts into the assembly fixture is at least partially, if not totally, automated. While such automated loading systems are relatively reliable, their occasional failure in misaligning a part when loading it into the assembly fixture and/or omitting the loading of a part into the assembly fixture altogether can result in lost revenue due to rejected assemblies and/or damage to the assembly fixture.
Accordingly, it is known to employ proximity switches, such a microswitches or the like, within the assembly fixture to confirm the correct loading of the parts. Specifically, the assembly fixture will include a proximity switch for each part to be loaded into the assembly fixture and the actuator arm of the switch will either directly contact the respective part or a mechanical plunger or other intermediate member will contact the part and act against the actuator arm of the switch, to signal that the part is loaded.
While such proximity switch systems work, they suffer from disadvantages in that a separate switch must be employed to detect each part to be loaded into the assembly fixture. While the need for multiple proximity switches increases the cost of the assembly fixture, they also increase the likelihood of downtime as the failure of any one of the multiple switches prevents use of the assembly fixture until the failed switch is replaced and, with several switches present on the assembly fixture, the probability of each switch failing is added to the probability of each other switch failing.
Further, in such prior art systems the proximity switch must either be located close to a respective part, and thus subjected to the hazards of the assembly operations such as heat, chemicals, impacts, etc. during the assembly operation or the above-mentioned plunger or other intermediate member must be employed between the proximity switch and the part location and the plunger or intermediate member is subjected to the above-mentioned hazards and/or other possible mechanical failures These hazards can result in failures of the operation of proximity switches and assembly downtime.
Also, prior art systems employing proximity switches may only be able to detect the presence or absence of a part and may not be able to identify when the part is incorrectly loaded within the assembly fixture.